Devices and methods disclosed herein relate generally to testing devices, and more specifically, to vane shear testing devices.
Vane shear testing devices are used in geotechnical engineering for determination of undrained shear strength, including undisturbed and remolded values. They are also used to study the effects of rotational rate on strength and as a tool for measurement of viscosity and other flow properties as a function of the rotational velocity or resulting strain rate in a variety of materials and sediments. The vane sensor is one of the main sensor configurations used in commercial rheometry products, for example, but not limited to, R/S Soft Solids Tester by BROOKFIELD® Engineering. Existing vane shear testing devices can be used, for example, but not limited to, (a) as handheld devices for rapid in-situ determination of the undrained shear strength of mostly surficial sediments in situ, and (b) in a bore-hole configuration in terrestrial and marine environments, for example, in FUGRO® Seaclam and FUGRO® Halibut systems. Additionally, vane testing can be used in the laboratory on sediment specimens retrieved in coring or drill cylinders. In this application, the sediment core is split either along its length or cut into several sub-sections normal to its long axis. Vane tests can be performed on the exposed soil surface utilizing a variety of vane devices. General engineering practice typically calls for testing for the strength parameters (undrained shear strength, residual/remolded strength) at a rotation rate of 60-90 deg/min (ASTM Standard. (2005)). See “D4648 Standard Test Method for Laboratory Miniature Vane Shear Test for Saturated Fine-Grained Clayey Soil.” ASTM International, West Conshohocken, Pa.
Rheometers are tools similar to vane shear devices (in certain configurations) and are used primarily in determining viscous parameters of fluids. Some rheometers, for example, R/S Soft Solids Tester by BROOKFIELD® Engineering, are adapted for testing viscous and yield properties of soft solids by utilizing a vane-shaped sensor. These instruments, however, test materials that are not normally encountered in natural environments, for example, materials that are typical to geotechnical investigations of either terrestrial or marine sediments. Thus, these instruments can be limited in rotational velocity and maximum torque capacity. These limitations could make them insufficient for certain types of geotechnical media and specific testing conditions. Further, devices characterized by variable rate torque application can be limited by the maximum rotational velocity that can be attained and the maximum torque that can be applied, limiting the use of these devices, especially for applications such as impact penetration and burial of objects in marine sediments.
What is needed is an apparatus for measuring shear strength and viscosity of sediments that extends both the maximum rotational rate attainable and the maximum torque sustainable, and includes a high data acquisition rate and data storage.